Epidemiological evidence suggests that the social environments of African Americans are rife with psychological stressors and challenging situations. Day to day encounters with life stressors lead to virtually countless physiological changes and sequelae. These physiological consequences may have inherent clinical significance, as in the cases of blood pressure changes, or they may provide insight into the status of an individual's psychological neurological state. Thanks to continuing breakthroughs, researchers have the capacity to measure an expanding panoply of physiological responses both in the laboratory and in the field. In addition, the cardiac systolic time interval, pre-ejection period (PEP), and the variability of heart rate reflected in the respiratory sinus arrythmia (RSA), appear to provide indices of sympathetic and parasympathetic nervous system input to the heart respectively. Researchers can assess both quite readily, in a non-invasive fashion. Here we propose two studies effects of stress and daily life events on cardiac activity in African American samples. The cardiac measures are not taken as indicators of disease, rather they are used to derive indices of underlying changes in autonomic nervous system activity. We will employ personality measures of hostility, cultural orientation and mood as predictors of cardiac activity while individuals carry out daily life functions. College students will serve as participants in the first investigation. Staff and faculty members at Howard University will constitute the principal source of data for the second. In addition to measures of PEP and RSA, impedance cardiographic measures of cardiac output, contractile force, stroke volume and left ventricular ejection time will constitute the primary dependent measures. Initially these will be obtained in the laboratory as participants encounter a battery of psychological tests of cardiac reactivity. These tests include rotary pursuit, visual search, and viewing and imaging socially noxious situations. Subsequently, impedance measures will be obtained during a 8- hour field assessment. In this phase, of the studies, participants will report moods and activities periodically. The studies will test the utility of a hierarchical regression model where personality variables including moderated measures of hostility, mood, cultural orientation, along with laboratory reactivity scores serves as predictors of cardiac activity recorded under ambulatory conditions. These studies are designed to clarify complex relationships between personality and laboratory cardiac reactivity, and the cardiac status of individuals engaged in daily activities. Thus they will contribute to our ability to forecast which individuals in this population are most vulnerable to the ravages of stressful environments.